Discussion Reproduction controlled exclusively by fire; trees occur in even-aged stands dating back to most recent fire. Unburned knobcone pine cones remain closed even after trees have decayed and fallen. Cones are sealed with a hard resin that requires high temperatures to liquefy, boil, and vaporize. Cone scales open gradually following heating, when the ground has cooled. Cones often remain closed for many years until a fire opens them and allows reseeding, as a result cones may become embedded in the trunk as the tree grows. Seeds enclosed in cones for 27 to 60 years have proved viable.